1. Field of the Invention
This invention relates to regulating the voltage of an integrated circuit that has an associated package inductance and a variable current demand.
2. Description of Background Art
High-speed microprocessors are increasingly being designed to operate at a low operating voltage and with tight tolerances on acceptable power supply voltage. In particular, individual semiconductor devices and critical logical paths must be able to withstand worst-case voltage variations.
The current demands of a high-speed microprocessor circuit may change rapidly, making it difficult to control the on-chip voltage due to the significant package inductance of a packaged microprocessor circuit. Common package inductance values limit the ability of the package inductor to respond to changes in current demand in time scales less than about 10 nanoseconds. One conventional approach to this problem is to use passive decoupling capacitors to reduce the effect of current changes on microprocessor operating voltage. However, decoupling capacitors require significant die area, particularly if they are to be scaled to permit tight voltage regulation for large, sudden variations in current demand, such as multi-cycle changes in current demand associated with changes in the current required by the microprocessor for multiple clock cycles, such as changes in logic current. Additionally, conventional decoupling capacitors may have difficulty responding to abrupt, multi-cycle changes in current demand.
Therefore what is needed is an improved method of regulating the voltage of a microprocessor associated with changes in current demand of the microprocessor.